Many cancer cells as well as some healthy cells are killed by the key base in DNA.
You can use resonance forms to explain your answer.
One of the bases in DNA is thymine.
The box at the side of the page shows the structure of 5-fluorouracil.
Furan is an aromatic five-membered Heterocycle similar to pyrrole, but in furan the to acid rain, because of the release of SO2 from the coal.
Heteroatom is the difference between nitrogen and oxygen.
The oxygen atom has two lone pairs of electrons, as shown in the classical structure for furan.
67 kJ>mol cleaner-burning product has a resonance energy of Furan.
Pyrrole, furan, and thiophene are isoelectronic.
The resonance energy of thiophene is 121 kJ>mol.
Explain why each compound is aromatic.
Pyrrole and furan are examples.
B3N3H6 is a stable compound.
Explain why borazole is aromatic.
The simplest fused aromatic compound is Naphthalene.
We use one of the Kekule resonance structures or the circle notation for the aromatic rings to represent naphthalene.
There are two aromatic rings in naphthalene.
Two iso lated aromatic rings have 6 pi electrons in them.
The smaller amount of electron density gives naphthalene less resonance energy than benzene.
The compounds become more reactive as the number of rings increases.
There is a resonance energy of 347 kJ>mol or 84 kcal>mol per aromatic ring.
There is a slightly higher resonance energy of 381 kJ>mol for phenanthrene.
Each of these compounds has only 14 pi electrons in its three aromatic rings.
Anthracene and phenan threne can undergo addition reactions that are more characteristic of their polyene relatives because they are not as stable as benzene.
Anthracene undergoes 1,4-addition at the 9- and 10-positions to give a product with two isolated, fully aromatic benzene rings.
phenanthrene is added at the 9- and 10-positions to give a product with two aromatic rings.
There are two additions shown.
9-bromophenanthrene results when the product from (c) is heated.
There is a mechanism for this.
The black material in diesel exhaust has more fused rings than anthracene and phenanthrene, and they have less resonance because of small particles that are rich energy per ring.
Most of the large PAHs must be drawn with polynuclear aromatic hydrocarbons.
Three compounds are present in tobacco smoke.
These compounds are so hazardous that laboratories must install special containment facilities to work with them, yet smokers expose their lung tissues to them every time they smoke a cigarette.
Its effects appear to be caused by its exposure to arene oxides, which can be attacked by DNA.
The resulting derivatives can't be transcribed.
They cause errors that cause the genes to change.
One of the oldest forms of pure carbon is graphite.
The stability of the old and new forms of carbon is dependent on aromaticity.
We don't usually think of carbon as an organic compound.
"Amorphous carbon" means charcoal, soot, coal, and carbon black.
Most of the mate rials are microcrystalline.
Small particle sizes and large surface areas are what they are characterized by.
The small particles absorb gases and solutes from solution and form strong, stable dispersions in polymers, such as the dispersion of carbon black in tires.
The hardest naturally occurring substance is diamond.
Diamond has a three-dimensional lattice with carbon atoms linked together.
The lattice extends throughout the crystal so that a diamond is one giant molecule.
They are unable to carry a current.
Diamond is a lattice of carbon atoms.
There are layers of aromatic rings.
A single layer of Graphene is one atom thick.
The distance between layers is 3.35 A, which is twice the van der Waals radius for carbon, suggesting there is little or no bonding between layers.
The layers can slide across each other, making it a good lubricant.
It is a good electrical conductor parallel to the layers, but it resists electrical currents when they are parallel to the layers.
We think of each layer of graphite as a lattice of aromatic rings.
There are no bonds between layers and all the valences are satisfied.
The layers are held together by only van der Waals forces.
The pi electrons within a layer can conduct electrical currents parallel to the layer, but electrons cannot easily jump between layers, so they are resistive to the layers.
The conversion of diamond to graphite is very slow for those who have invested in it.
The higher density of diamond suggests that it might be con verted to diamond under high pressures.
Small industrial diamonds can be made using catalysts such as Cr and Fe, which can be made using pressures over 125,000 atm.
The University of Manchester's Andre Geim and Konstantin Novoselov won the 2010 Nobel Prize in physics for their work on Graphene, which is a single layer of graphite one atom thick.
They pulled one layer away from the surface of the piece.
Graphene is an excellent conductor.
If it can ever be mass-produced in large sheets, it holds great promise for touch-screen monitors.
A molecule of formula C60 was isolated from the soot produced by using a laser and an electric arcs.
There are only two types of bonds in C60, and it has only one type of carbon atom.
A soccer ball has the same structure as C60, with each atom representing a carbon atom.
The carbon atoms are the same.
Two six-membered rings and one five-membered ring are served by each carbon.
There are two types of bonds, the bonds that are shared by a five-membered ring and a six-membered ring, and the bonds shared between two six-membered rings.
It appears that the six-membered rings are aromatic, but the double bonds are partially hidden between the six-membered rings.
Some of the addition reactions of alkenes can be seen in the double bonds.
Half of the C60 sphere is fused to a cylinder made of six- membered rings.
The strength-to-weight ratio and the fact that they are only along the length of the tube have aroused interest.
Each year, thousands of tons of nanotubes are produced.
They are added to the cured polymers to make them stronger.
They are used to promote bone growth in tissue cultures and as tips for atomic force microscope probes.
A five-membered ring and two six-membered rings are bridgehead carbons.
A cylinder made of aromatic six-membered rings is called a nanotube.
Half of a C60 sphere is at the end of the tube.
The structure to curve at the end of the tube is caused by the five membered buckyball.
Purine is a compound with rings that share two atoms and a bond between them.
The properties of fused-ring Heterocycles are similar to those of the simple Heterocycles.
In nature, fused compounds are used to treat a wide variety of illnesses.
A member of the fluoroquinolone class is ciprofloxacin.
Benzene derivatives have been used as industrial reagents for over 100 years.
Many of their names are from the past.
Many compounds are derivatives of benzene, with their substituents being attached to an alkane.
The substitution in disubstituted benzenes can be specified with numbers.
Numbers are used to indicate the positions of three or more substituents.
If the substitution pattern is functional group that defines the base name, a structure to be C1 is assumed.
Many disubstituted benzenes have historical names.
There is no obvious connection between the structure of the molecule and some of these.
Name all the benzenes that have between one and six chlorine atoms.
Table 16-1 contains the melting points, boiling points, and densities of benzene and some derivatives.
Benzene derivatives have higher melting points than aliphatic compounds because they are more symmetrical.
Para disubstituted benzenes pack better into crystals and have higher melting points than the ortho and meta isomers.
The boiling points of many benzene derivatives are related to their dipole moments.
The lowest boiling point for Dichlorobenzene and the lowest boiling point for the Mothballs is zero.
The two compounds are boiling.
Dichlorobenzene has the lowest boiling point because it is the highest melting point of the dichlorobenzenes.
The benzenes are denser than water.
C stretch around 1600 cm-1 is a characteristic of aromatic compounds.
The aromatic bond order is only about 1 12 so this is a lower C stretching frequency.
The aromatic bond vibrates at a lower Frequency because it is less stiff than a normal double bond.
H is stretching just above 3000 cm-1.
The compounds labeled Compounds 4, 5, and 7 show aromatic rings.
The aromatic ring current protects the 1H NMR signals around d 7 to d 8.
The aromatic protons absorb around 7.2 d in benzene.
The signals may be moved further downfield bydrawing groups such as carbonyl, nitro, or cyano groups.
The aromatics that are ortho or meta split.
The spin-spin splitting constants are used for ortho protons and meta protons.
Carbon atoms absorb between 120 and 150 in the 13C spectrum.
The presence of an aromatic ring is usually confirmed by the combination of 13C NMR with 1H NMR or IR spectroscopy.
A resonance-stabilized benzylic cation can be given by the cleavage of a benzylic bond.
The aromatic tropylium ion may be given by rearranging the benzyl cation.
The ultraviolet spectrum of aromatic compounds is different from that of nonaromatic polyenes.
There are three absorptions in the ultraviolet region for benzene: an intense band at lmax of 184 nm, a moderate band at lmax of 204 nm, and a characteristic low-intensity band of multiple absorptions centered around 254 nm.
There are three major bands in the benzene spectrum.
If benzene were always an unperturbed, perfectly hexagonal structure, the weaker band at 204 nm would correspond to a "forbidden" transition.
The molar absorptivities are usually 200 to 300.
Most of the characteristics of benzene are shown in simple benzene derivatives, which are in the moderate band and benzenoid band.
The values of lmax are increased by about 5 nm by the use of alkyl and halogen substituents.
The isomer of this compound is rearranged when it is treated with a strong acid.
Suggest a structure for the isomeric product.
An organic compound is not aromatic.
Different forms of carbon are referred to as allotropic forms.
There are alternating single and double bonds.
The compound is characterized by a large resonance energy.
The benzene ring is a structural unit for aromatic hydrocarbons.
The aromatic group that remains after taking a hydrogen atom off an aromatic ring is the generic alkyl group.
The band is characterized by multiple sharp absorptions.
The arrangement of five-membered and six-membered rings is similar to a dome.
Orbitals have the same energy.
According to Marilyn Monroe, a girl's best friend.
A generic term for carbon clusters similar to C60 and compounds related to them.
One or more of the ring atoms in a compound is not carbon.
A compound that has a large resonance energy and is aromatic.
A classical formula for an aromatic compound.
A carbon tube is a cylinder of six-membered rings and half a C60 sphere.
There is a relationship on a ring.
There is a relationship on a benzene ring.
There is a relationship on a benzene ring.
The benzene ring is a substituent on another molecule.
The energy diagram of the MOs of a regular, completely conjugated system has the same shape as the compound, with one edge at the bottom.
There is a polynuclear aromatic Heterocycle.
The stabilization provided by delocalization is more than that provided by a local structure.
The extra stabilization provided by the delocalization of the electrons in the aromatic ring is called resonance energy.
Each skill is followed by problem numbers.
If you use the Huckel's rule, you can predict whether a given ion or annulene will be a problem.
If nitrogen's lone pairs are used in the aromatic system, you can determine whether the nitrogen atom is weakly basic or strongly basic.
The theory of aromatic compounds can be used to explain the properties of fused aromatic systems.
Draw their structures from the names.
Predict the properties of aromatic compounds and the effects that aromatic rings have on neighboring parts of the molecule.
To determine the structures of aromatic compounds, use IR, NMR, UV, and mass spectrums.
Problems 16-38, 44, 45, 46, 48 are given an aromatic compound.
The structure of each compound can be drawn.
Four compounds are shown.
One of the compounds reacts more quickly, or with a more favorable equilibrium constant, in each pair.
Explain the enhanced reactivity.
One of the hydrocarbons is more acidic than the others.
Explain why it is acidic.
There was no proof that benzene was a six-membered ring in Kekule's time.
The structure was determined using the known numbers of monosubstituted and disubstituted benzenes and the knowledge that benzene did not react similarly to a normal alkene.
There are six hydrogen atoms in each structure.
Draw all the possible monobrominated derivatives that could result from a random substitution of one hydrogen with a bromine.
Benzene had only one monobromo derivative.
Draw all the possible dibromo derivatives for the structures that only had one monobromo derivative.
At the time resonance theory was unknown, Benzene was known to have three dibromo derivatives.
Determine which structure was most consistent with what was known about benzene at that time: Benzene gives one monobrominated derivative and three dibrominated derivatives, and it gives negative chemical tests for alkene.
The ion and molecule are grouped by similar structures.
Give the number of pi electrons in the ring to the aromatic species.
Nitrogen atoms are included in each of the following Heterocycles.
Classify the nitrogen atom according to the availability of its lone pair of electrons.
Some of the compounds have aromatic properties, but others do not.
Explain why they are aromatic.
Predict which nitrogen atoms are more basic than water.
Simple alkyl intermediates are more stable than benzylic cations, anions, and radicals.
Use resonance forms to show the delocalization of the positive charge, unpaired electron, and negative charge of the benzyl cation, radical, and anion.
In the presence of light, toluene reacts with bromine to give benzyl bromide.
There is a mechanism for this reaction.
You can use a drawing of the transition state to explain your answer.
Adding a third group and figuring out how many isomers are formed is one of the methods used by Korner.
Two isomers are formed when xylene is nitrated.
A chemist isolated an aromatic compound from a formula.
He nitrated this compound and made three isomers.
The structure should be consistent with the spectrum and the additional information provided.
The formula shown in the analysis is C8H7OCl.
There is a moderate absorption at 1602 cm-1 and a strong absorption at 1690 cm-1 in the IR spectrum.
The Diels-Alder reaction requires a Kekule structure that shows how the reactive positions of anthracene are at the end of a diene.
A common organic lab experiment is the Diels-Alder reaction of anthracene with maleic anhydride.
Biphenyl has a structure.
dianions of hydrocarbons are very rare.
A dianion of formula [C9H9]2 is formed by the reaction of the following hydrocarbons with two equivalents of butyllithium.
Give a structure for this dianion and explain why it forms so quickly.
The structure of a ribonucleoside is shown here.
The four bases are uracil, guanine, and adenine.
Determine which bases are aromatic.
Which nitrogen atoms are basic?
A student found an old bottle in the stockroom.
She obtained the following mass after smelling a pleasant odor.
On shaking with D2O, the peak of the NMR disappears.
Show how your structure is consistent with the spectrum.
The resulting ion is stable.
It has been separated into enantiomers.
The optical rotation is enormous.
Explain why the rotation is large and speculate as to why it is so active.
To see the relative energies of all the MO's, draw the energy diagram and show which orbitals the electrons would occupy in the ground state.
Predict whether the ion is aromatic or not.
The hydrogens in pyridine are shown.
The ortho protons are deshielded to d 8.60, which is a typical aromatic chemical shift.
A family of compounds called chlorophyll is present in green plants.
The energy in the sun can be used to convert carbon dioxide and water into sugars.
The chlorin is a large-ring magnesium complex.
The large pi system makes it aromatic.
Many properties, including aromaticity, have been probed with the use of NMR.